如何获取方法（.NET）中使用的字段？

Question

在.NET中，使用反射如何获取方法中使用的类变量？

例如：

class A
{
    UltraClass B = new(..);
    SupaClass C = new(..);

    void M1()
    {
        B.xyz(); // it can be a method call
        int a = C.a; // a variable access
    }
}

注意： GetClassVariablesInMethod（M1 MethodInfo）返回B和C变量。 通过变量，我指的是该特定变量的值和/或类型和构造函数参数。

Answer 1

有很多不同的答案，但由于没有一个人对我有吸引力，所以这是我的。它正在使用我的Reflection based IL reader。

这是一个方法，用于检索方法使用的所有字段：

static IEnumerable<FieldInfo> GetUsedFields (MethodInfo method)
{
    return (from instruction in method.GetInstructions ()
           where instruction.OpCode.OperandType == OperandType.InlineField
           select (FieldInfo) instruction.Operand).Distinct ();
}

Answer 2

这是正确答案的完整版本。这使用了来自其他答案的材料，但包含了一个重要的错误修正，没有人发现。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Reflection.Emit;

namespace Timwi.ILReaderExample
{
    public class ILReader
    {
        public class Instruction
        {
            public int StartOffset { get; private set; }
            public OpCode OpCode { get; private set; }
            public long? Argument { get; private set; }
            public Instruction(int startOffset, OpCode opCode, long? argument)
            {
                StartOffset = startOffset;
                OpCode = opCode;
                Argument = argument;
            }
            public override string ToString()
            {
                return OpCode.ToString() + (Argument == null ? string.Empty : " " + Argument.Value);
            }
        }

        private Dictionary<short, OpCode> _opCodeList;

        public ILReader()
        {
            _opCodeList = typeof(OpCodes).GetFields().Where(f => f.FieldType == typeof(OpCode)).Select(f => (OpCode) f.GetValue(null)).ToDictionary(o => o.Value);
        }

        public IEnumerable<Instruction> ReadIL(MethodBase method)
        {
            MethodBody body = method.GetMethodBody();
            if (body == null)
                yield break;

            int offset = 0;
            byte[] il = body.GetILAsByteArray();
            while (offset < il.Length)
            {
                int startOffset = offset;
                byte opCodeByte = il[offset];
                short opCodeValue = opCodeByte;
                offset++;

                // If it's an extended opcode then grab the second byte. The 0xFE prefix codes aren't marked as prefix operators though.
                if (opCodeValue == 0xFE || _opCodeList[opCodeValue].OpCodeType == OpCodeType.Prefix)
                {
                    opCodeValue = (short) ((opCodeValue << 8) + il[offset]);
                    offset++;
                }

                OpCode code = _opCodeList[opCodeValue];

                Int64? argument = null;

                int argumentSize = 4;
                if (code.OperandType == OperandType.InlineNone)
                    argumentSize = 0;
                else if (code.OperandType == OperandType.ShortInlineBrTarget || code.OperandType == OperandType.ShortInlineI || code.OperandType == OperandType.ShortInlineVar)
                    argumentSize = 1;
                else if (code.OperandType == OperandType.InlineVar)
                    argumentSize = 2;
                else if (code.OperandType == OperandType.InlineI8 || code.OperandType == OperandType.InlineR)
                    argumentSize = 8;
                else if (code.OperandType == OperandType.InlineSwitch)
                {
                    long num = il[offset] + (il[offset + 1] << 8) + (il[offset + 2] << 16) + (il[offset + 3] << 24);
                    argumentSize = (int) (4 * num + 4);
                }

                // This does not currently handle the 'switch' instruction meaningfully.
                if (argumentSize > 0)
                {
                    Int64 arg = 0;
                    for (int i = 0; i < argumentSize; ++i)
                    {
                        Int64 v = il[offset + i];
                        arg += v << (i * 8);
                    }
                    argument = arg;
                    offset += argumentSize;
                }

                yield return new Instruction(startOffset, code, argument);
            }
        }
    }

    public static partial class Program
    {
        public static void Main(string[] args)
        {
            var reader = new ILReader();
            var module = typeof(Program).Module;
            foreach (var instruction in reader.ReadIL(typeof(Program).GetMethod("Main")))
            {
                string arg = instruction.Argument.ToString();
                if (instruction.OpCode == OpCodes.Ldfld || instruction.OpCode == OpCodes.Ldflda || instruction.OpCode == OpCodes.Ldsfld || instruction.OpCode == OpCodes.Ldsflda || instruction.OpCode == OpCodes.Stfld)
                    arg = module.ResolveField((int) instruction.Argument).Name;
                else if (instruction.OpCode == OpCodes.Call || instruction.OpCode == OpCodes.Calli || instruction.OpCode == OpCodes.Callvirt)
                    arg = module.ResolveMethod((int) instruction.Argument).Name;
                else if (instruction.OpCode == OpCodes.Newobj)
                    // This displays the type whose constructor is being called, but you can also determine the specific constructor and find out about its parameter types
                    arg = module.ResolveMethod((int) instruction.Argument).DeclaringType.FullName;
                else if (instruction.OpCode == OpCodes.Ldtoken)
                    arg = module.ResolveMember((int) instruction.Argument).Name;
                else if (instruction.OpCode == OpCodes.Ldstr)
                    arg = module.ResolveString((int) instruction.Argument);
                else if (instruction.OpCode == OpCodes.Constrained || instruction.OpCode == OpCodes.Box)
                    arg = module.ResolveType((int) instruction.Argument).FullName;
                else if (instruction.OpCode == OpCodes.Switch)
                    // For the 'switch' instruction, the "instruction.Argument" is meaningless. You'll need extra code to handle this.
                    arg = "?";
                Console.WriteLine(instruction.OpCode + " " + arg);
            }
            Console.ReadLine();
        }
    }
}

Answer 3

您需要获取MethodInfo。调用GetMethodBody（）以获取方法体结构，然后在其上调用GetILAsByteArray。将该字节数组转换为易于理解的IL流。

粗略地说

public static List<Instruction> ReadIL(MethodInfo method)
{
    MethodBody body = method.GetMethodBody();
    if (body == null)
        return null;

    var instructions = new List<Instruction>();
    int offset = 0;
    byte[] il = body.GetILAsByteArray();
    while (offset < il.Length)
    {
        int startOffset = offset;
        byte opCodeByte = il[offset];
        short opCodeValue = opCodeByte;
        // If it's an extended opcode then grab the second byte. The 0xFE
        // prefix codes aren't marked as prefix operators though. 
        if (OpCodeList[opCodeValue].OpCodeType == OpCodeType.Prefix
            || opCodeValue == 0xFE)
        {
            opCodeValue = (short) ((opCodeValue << 8) + il[offset + 1]);
            offset += 1;
        }
        // Move to the first byte of the argument.
        offset += 1;

        OpCode code = OpCodeList[opCodeValue];

        Int64? argument = null;
        if (code.ArgumentSize() > 0)
        {
            Int64 arg = 0;
            Debug.Assert(code.ArgumentSize() <= 8);
            for (int i = 0; i < code.ArgumentSize(); ++i)
            {
                Int64 v = il[offset + i];
                arg += v << (i*8);
            }
            argument = arg;
            offset += code.ArgumentSize();
        }

        var instruction = new Instruction(startOffset, code, argument);
        instructions.Add(instruction);
    }

    return instructions;
}

其中OpCodeList是通过

构建的

OpCodeList = new Dictionary<short, OpCode>();
foreach (var opCode in typeof (OpCodes).GetFields()
                       .Where(f => f.FieldType == typeof (OpCode))
                       .Select(f => (OpCode) f.GetValue(null)))
{
    OpCodeList.Add(opCode.Value, opCode);
}

然后，您可以确定哪些指令是IL属性调用或成员变量查找或您需要的任何指令，然后通过GetType（）解析.Module.ResolveField。

（警告代码上面或多或少的工作，但是我从一个更大的项目中扯下来，所以可能会遗漏一些细节）。

编辑：参数大小是OpCode上的一种扩展方法，只是使用查找表来查找相应的值

public static int ArgumentSize(this OpCode opCode)
{
  Dictionary<OperandType, int> operandSizes 
           = new Dictionary<OperandType, int>()
                 {
                    {OperandType.InlineBrTarget, 4},
                    {OperandType.InlineField, 4},
                    {OperandType.InlineI, 4},
                    // etc., etc.
                 };
  return operandSizes[opCode.OperandType];
}

您会在ECMA 335找到尺寸，您还需要查看操作码以查找要搜索的操作码以查找您要查找的电话。

Answer 4

Reflection主要是用于检查元数据的API。你要做的是检查原始IL，这不是反射支持的功能。反射只返回IL作为原始字节[]，必须手动检查。

Answer 5

@Ian G：我已经从ECMA 335编制了列表，发现我可以使用

List<MethodInfo> mis = 
    myObject.GetType().GetMethods().Where((MethodInfo mi) =>
        {
            mi.GetCustomAttributes(typeof(MyAttribute), true).Length > 0;
        }
    ).ToList();
foreach(MethodInfo mi in mis)
{
    List<Instruction> lst = ReflectionHelper.ReadIL(mi);
    ... find useful opcode
    FieldInfo fi = mi.Module.ResolveField((int)usefulOpcode.Argument);
    object o = fi.GetValue(myObject);
    ...
}

如果有人需要，操作码长度列表就在这里：

Dictionary<OperandType, int> operandSizes
= new Dictionary<OperandType, int>()
{
    {OperandType.InlineBrTarget, 4},
    {OperandType.InlineField, 4},
    {OperandType.InlineI, 4},
    {OperandType.InlineI8,8},
    {OperandType.InlineMethod,4},
    {OperandType.InlineNone,0},
    {OperandType.InlineR,8},
    {OperandType.InlineSig,4},
    {OperandType.InlineString,4},
    {OperandType.InlineSwitch,4},
    {OperandType.InlineTok,4},
    {OperandType.InlineType,4},
    {OperandType.InlineVar,2},
    {OperandType.ShortInlineBrTarget,1},
    {OperandType.ShortInlineI,1},
    {OperandType.ShortInlineR,4},
    {OperandType.ShortInlineVar,1}
};